// NSRecords returns NS records from etcd.
func (s *server) NSRecords(q dns.Question, name string) (records []dns.RR, extra []dns.RR, err error) {
services, err := s.backend.Records(name, false)
if err != nil {
return nil, nil, err
}
services = msg.Group(services)
for _, serv := range services {
ip := net.ParseIP(serv.Host)
switch {
case ip == nil:
return nil, nil, fmt.Errorf("NS record must be an IP address")
case ip.To4() != nil:
serv.Host = msg.Domain(serv.Key)
records = append(records, serv.NewNS(q.Name, serv.Host))
extra = append(extra, serv.NewA(serv.Host, ip.To4()))
case ip.To4() == nil:
serv.Host = msg.Domain(serv.Key)
records = append(records, serv.NewNS(q.Name, serv.Host))
extra = append(extra, serv.NewAAAA(serv.Host, ip.To16()))
}
}
return records, extra, nil
}
func (s *server) TXTRecords(q dns.Question, name string) (records []dns.RR, err error) {
services, err := s.backend.Records(name, false)
if err != nil {
return nil, err
}
services = msg.Group(services)
for _, serv := range services {
if serv.Text == "" {
continue
}
records = append(records, serv.NewTXT(q.Name))
}
return records, nil
}
func (s *server) CNAMERecords(q dns.Question, name string) (records []dns.RR, err error) {
services, err := s.backend.Records(name, true)
if err != nil {
return nil, err
}
services = msg.Group(services)
if len(services) > 0 {
serv := services[0]
if ip := net.ParseIP(serv.Host); ip == nil {
records = append(records, serv.NewCNAME(q.Name, dns.Fqdn(serv.Host)))
}
}
return records, nil
}
// SRVRecords returns SRV records from etcd.
// If the Target is not a name but an IP address, a name is created.
func (s *server) SRVRecords(q dns.Question, name string, bufsize uint16, dnssec bool) (records []dns.RR, extra []dns.RR, err error) {
services, err := s.backend.Records(name, false)
if err != nil {
return nil, nil, err
}
services = msg.Group(services)
// Looping twice to get the right weight vs priority
w := make(map[int]int)
for _, serv := range services {
weight := 100
if serv.Weight != 0 {
weight = serv.Weight
}
if _, ok := w[serv.Priority]; !ok {
w[serv.Priority] = weight
continue
}
w[serv.Priority] += weight
}
lookup := make(map[string]bool)
for _, serv := range services {
w1 := 100.0 / float64(w[serv.Priority])
if serv.Weight == 0 {
w1 *= 100
} else {
w1 *= float64(serv.Weight)
}
weight := uint16(math.Floor(w1))
ip := net.ParseIP(serv.Host)
switch {
case ip == nil:
srv := serv.NewSRV(q.Name, weight)
records = append(records, srv)
if _, ok := lookup[srv.Target]; ok {
break
}
lookup[srv.Target] = true
if !dns.IsSubDomain(s.config.Domain, srv.Target) {
log.Printf("skydns: target %q is not sub of %q, looking up...", srv.Target, s.config.Domain)
m1, e1 := s.Lookup(srv.Target, dns.TypeA, bufsize, dnssec)
if e1 == nil {
extra = append(extra, m1.Answer...)
}
m1, e1 = s.Lookup(srv.Target, dns.TypeAAAA, bufsize, dnssec)
if e1 == nil {
// If we have seen CNAME's we *assume* that they are already added.
for _, a := range m1.Answer {
if _, ok := a.(*dns.CNAME); !ok {
extra = append(extra, a)
}
}
}
break
}
// Internal name, we should have some info on them, either v4 or v6
// Clients expect a complete answer, because we are a recursor in their
// view.
addr, e1 := s.AddressRecords(dns.Question{srv.Target, dns.ClassINET, dns.TypeA},
srv.Target, nil, bufsize, dnssec, true)
if e1 == nil {
extra = append(extra, addr...)
}
case ip.To4() != nil:
serv.Host = msg.Domain(serv.Key)
records = append(records, serv.NewSRV(q.Name, weight))
extra = append(extra, serv.NewA(serv.Host, ip.To4()))
case ip.To4() == nil:
serv.Host = msg.Domain(serv.Key)
records = append(records, serv.NewSRV(q.Name, weight))
extra = append(extra, serv.NewAAAA(serv.Host, ip.To16()))
}
}
return records, extra, nil
}
func (s *server) AddressRecords(q dns.Question, name string, previousRecords []dns.RR, bufsize uint16, dnssec, both bool) (records []dns.RR, err error) {
services, err := s.backend.Records(name, false)
if err != nil {
return nil, err
}
services = msg.Group(services)
for _, serv := range services {
ip := net.ParseIP(serv.Host)
switch {
case ip == nil:
// Try to resolve as CNAME if it's not an IP, but only if we don't create loops.
if q.Name == dns.Fqdn(serv.Host) {
// x CNAME x is a direct loop, don't add those
continue
}
newRecord := serv.NewCNAME(q.Name, dns.Fqdn(serv.Host))
if len(previousRecords) > 7 {
log.Printf("skydns: CNAME lookup limit of 8 exceeded for %s", newRecord)
// don't add it, and just continue
continue
}
if s.isDuplicateCNAME(newRecord, previousRecords) {
log.Printf("skydns: CNAME loop detected for record %s", newRecord)
continue
}
nextRecords, err := s.AddressRecords(dns.Question{Name: dns.Fqdn(serv.Host), Qtype: q.Qtype, Qclass: q.Qclass},
strings.ToLower(dns.Fqdn(serv.Host)), append(previousRecords, newRecord), bufsize, dnssec, both)
if err == nil {
// Only have we found something we should add the CNAME and the IP addresses.
if len(nextRecords) > 0 {
records = append(records, newRecord)
records = append(records, nextRecords...)
}
continue
}
// This means we can not complete the CNAME, try to look else where.
target := newRecord.Target
if dns.IsSubDomain(s.config.Domain, target) {
// We should already have found it
continue
}
m1, e1 := s.Lookup(target, q.Qtype, bufsize, dnssec)
if e1 != nil {
log.Printf("skydns: incomplete CNAME chain: %s", e1)
continue
}
// Len(m1.Answer) > 0 here is well?
records = append(records, newRecord)
records = append(records, m1.Answer...)
continue
log.Printf("skydns: incomplete CNAME chain for %s", name)
case ip.To4() != nil && (q.Qtype == dns.TypeA || both):
records = append(records, serv.NewA(q.Name, ip.To4()))
case ip.To4() == nil && (q.Qtype == dns.TypeAAAA || both):
records = append(records, serv.NewAAAA(q.Name, ip.To16()))
}
}
if s.config.RoundRobin {
s.RoundRobin(records)
}
return records, nil
}